Femtosecond UV-laser processing of sub-/spl mu/m holes in steel foils

Summary form only given. The advantages of femtosecond laser pulses for the precision drilling of holes in metals has been often demonstrated. Precise edges without ablation debris can be reached. In most cases Ti:sapphire lasers are used to produce holes with a diameter of some ten /spl mu/m down to some /spl mu/m. A UV-wavelength offers the possibility to improve the optical resolution by a factor of three compared to the Ti:sapphire wavelength and to achieve even sub-/spl mu/m holes with high aspect ratios. We used a fs-UV-laser system (248 nm, 500 fs, 10 mJ) to illuminate a pinhole of 12.5 /spl mu/m diameter. The diffracted light is focused by a Schwarzschild type reflective objective (36x, NA= 0.3) onto the sample surface.